Electronic sewing machine and presser foot particularly for buttonhole stitches and process for producing buttonhole stitches utilizing alternately operable sensor

Abstract

An electronic zigzag sewing machine is provided with a presser foot including a switch lever pivotable between a first and second position. During buttonhole stitching operation the switch lever remains in the first position, but it is shifted to the second position when either one of longitudinal ends of a buttonhole is detected. A photo-sensor is mounted to the presser foot to output a detection signal when the switch lever is in the second position. A pattern number designating a specific stitch pattern of the buttonhole stitches is renewed to the next in response to the detection signal from the photo-sensor. A control system is provided to nullify operation of the photo-sensor during production of bar tacks of the buttonhole stitches so that the pattern number is not renewed in areas of the bar tacks irrespective of output of the detection signal.

What is claimed is: 
     
       1. An electronic sewing machine comprising a controller for energizing the sewing machine; memory means for storing stitch control data for a plurality of stitch patterns including a buttonhole stitch pattern, each stitch pattern being assigned one or more pattern numbers;   stitch pattern select means for selecting a specific one of the stitch patterns, thereby generating corresponding pattern number or numbers;   pattern producing means for producing a selected stitch pattern in response to the stitch control data stored in said memory means for the corresponding pattern number or numbers;   and buttonhole sensor means for detecting longitudinal ends of a buttonhole to output a first signal when the buttonhole stitch pattern is being produced by said pattern producing means;   the improvement which further comprises a counter operated in response to said first signal to output a step-up signal;   pattern number renewing means operated in response to said step-up signal to set the pattern number to the next of the selected stitch patterns;   buttonhole stitch-over detecting means for stopping sewing machine operation and at the same time outputting a second signal when the buttonhole stitches have been completed;   discriminating means for outputting a third signal when discriminating the sewing machine is not in operation;   a safety means for setting the sewing machine to a safety condition in which the sewing machine operation is interrupted during receiving said first, second and third signals;   and cancel means for cancelling said safety condition of the sewing machine.   
     
     
       2. The sewing machine according to claim 1 wherein said counter is reset to output a reset signal to said pattern number renewing means, when receiving said first and third signal and when said second signal is not outputted, said pattern number renewing means being in response to said reset signal to reset the pattern number to the first one of the selected stitch pattern. 
     
     
       3. The sewing machine according to claim 1 wherein said buttonhole sensor means comprises a presser foot including a presser bar mounted to a machine housing; a workpiece presser for exerting a downwardly directing pressure onto a workpiece to be stitched and adapted to be moved together with the workpiece; first and second engaging members located in opposition to each other on said workpiece presser, a distance between said first and second engaging members being adjustable in correspondence to a button size; a switch lever having a portion engageable with said first and second engaging members, said switch lever being adapted to be positioned in a first position in which said portion is located between said first and second engaging members with no contact thereto and a second position in which said portion is in engagement with either one of said first and second engaging members; and a sensor means for detecting said switch lever being in the second position, thereby detecting a longitudinal end of the buttonhole. 
     
     
       4. The sewing machine according to claim 3 wherein said switch lever is shifted to the second position when said presser bar is released. 
     
     
       5. An electronic sewing machine comprising memory means for storing stitch control data for a plurality of stitch patterns including a buttonhole stitch pattern, the stitch control data for the buttonhole stitch pattern including a number of different pattern data to be sequentially read out; stitch pattern select means for selecting a specific one of the stitch patterns; first control means operated in response to the stitch control data stored in said memory means of a stitch pattern selected by said stitch pattern select means to produce stitches of the selected stitch pattern; sensor means for detecting longitudinal ends of the buttonhole, said first control means being operated to set the present pattern data to the next one when said sensor means detects one of the longitudinal ends of the buttonhole; and second control means for nullifying operation of said sensor means within bar tack stitch areas produced near the longitudinal ends of the buttonhole. 
     
     
       6. The sewing machine according to claim 5 wherein said second control means is operated by control data stored in said memory means together with the stitch control data for the buttonhole stitches. 
     
     
       7. The sewing machine according to claim 5 wherein said second control means comprises an electronic control circuit for nullifying intermittent on/off signals generated from said second control means. 
     
     
       8. A process for producing buttonhole stitches with an electronic sewing machine wherein plural series of stitch control data for the buttonhole stitches are sequentially read out from a memory unit to control a needle amplitude and a fabric feeding amount, one series of the stitch control data being set to the next series when a longitudinal end of the buttonhole is detected with sensor means, the improvement in which operation of said sensor means is annulled during stitching of portions of bar tacks produced at both longitudinal ends of the buttonhole. 
     
     
       9. A buttonhole presser foot used in combination with a zigzag sewing having a needle which is vertically reciprocable and laterally swingable, a presser bar mounted substantially in parallel with said needle and fabric feeding means for feeding a fabric placed on a machine bed in predetermined direction, said buttonhole presser foot comprising: a photo-impermeable supporting frame mounted detachably to the lower end of said presser bar;   a sliding member pivotably connected to the lower end of said supporting frame and including a needle penetrating hole;   a presser foot sole mounted slidably with respect to said sliding member and adapted to exert a downward pressure onto the fabric and cooperating with said fabric feeding means to feed the fabric;   a first engaging member secured to said presser foot sole;   a second engaging member attached to said presser foot sole, said second engaging member being slideable with respect to said presser foot sole so that a distance between said first and second engaging members is adjustable in accordance with a length of a buttonhole to be formed;   a switch lever pivotted to said supporting frame and having a first end engageable with either one of said first and second engaging members when the stitching operation reaches one longitudinal end of the buttonhole and a second end substantially encircled within said supporting frame;   photo-sensor means for detecting displacement of said second end of said switch lever activated when said first end comes into engagement with either one of said first and second engaging members.   
     
     
       10. The buttonhole presser foot according to claim 9 wherein said second end of said switch lever provides a light reflector and said photo-sensor means comprises a photo-impermeable casing secured to said supporting frame in a close vicinity thereto and light emitting means and light receiving means secured to said casing, said second end being positioned to reflect the light emitted from said light emitting means towards said light receiving means while producing the buttonhole, said position of said second end being displaced to interrupt the light reflection when said second end is displaced. 
     
     
       11. The buttonhole presser foot according to claim 9 wherein said second end of said switch lever provides a light path and said photo-sensor means comprises light emitting means and light receiving means secured within said supporting frame and opposed to each other with said second end put therebetween, said second end being positioned to pass the light emitted from said light emitting means through said light path towards said light receiving means while producing the buttonhole, said position of said second end being displaced to interrupt the light passage when said second end is displaced.